Here is my guess: I don't think it is plug rleated UNLESS a plug wasn't check for a proper gap.

It could instead be related to a wire or connector.

I hate to admit this ...... OK here goes ..... I was going crazy trying to figure out why the 300E idled roughly every so often. When I recently changed the plugs, the loose spark plug connection on cylinder # was the obvious reason.

Check each connector. Twist them gently and tug on 'em to make sure they are on securely.

Although I don't have any pictures of this, the O2 sensor is a three wire Bosch unit that the dealer wants over $200 for. After some careful research, I found that the 1990 Ford Mustang 5.0 uses the exact Bosch 3 wire O2 sensor, but with a different plug on the end. I bought the Mustang O2 sensor for $36 and cut the plug off my old O2 sensor and spliced it onto the new O2 sensor. Works perfect!

Originally posted by brookspw I'm going in tomorrow to have him check it out. He said he also "leaned it out" and maybe he went to far. I am assuming he means fuel mixture -- by what method would he have done that?

Ditto on that.. Mide did the same thing when I leaned it out too much... By adjusting the Lambda...